1. Technical Field
The invention relates to a driving control device using an electro-mechanical converting element, a portable optical apparatus and a driving control method.
2. Description of the Related Art
Various actuators using a piezoelectric element have been proposed in the related art. For example, an actuator using a piezoelectric element for focus driving of a lens of a camera has been proposed (refer to Japanese Patent No. 2633066 (corresponding to U.S. Pat. No. 5,225,941)). In such an actuator, it is common that supply of driving pulses to the piezoelectric element is controlled to cause the piezoelectric element to expanded and contract so that the expansion rate and contraction rate of the piezoelectric element along a predetermined direction are different, thereby vibrating a shaft member for lens driving along the predetermined direction, and minutely moving the lens, which frictionally engages with the shaft member along the predetermined direction.
However, since the actuator is configured such that the piezoelectric element is caused to expand and contract so that the expansion rate and contraction rate of the piezoelectric element along the predetermined direction are different, thereby vibrating the shaft member along the predetermined direction and minutely moving the lens which frictionally engages with the shaft member, it is difficult to move the lens just a distance, which is in proportion to a driving pulse number.
In order to improve the accuracy of the focus driving of a lens in view of the above circumstance, JP Hei. 11-356070A (corresponding to U.S. Pat. No. 6,249,093) discloses a technique in which a traveling speed of the lens is obtained by detecting a traveling distance of the lens, and the supply stop time of driving pulses for driving of the lens is controlled so that the traveling speed of the lens becomes a predetermined target speed. In this technique, since the traveling speed of the lens is obtained every moment while focus driving of the lens is performed and high-speed control by multi-tasking is performed so that the traveling speed of the lens becomes a predetermined target speed, high-precision focus driving control can be expected except for an initial stage of the control concerned.
However, since JP Hei. 11-356070A requires high-speed control by multi-tasking, a control device equipped with a multi-task CPU is needed. The high-speed control cannot be realized in a control device equipped with only an inexpensive single task CPU. Moreover, since the supply stop time of driving pulses is controlled simultaneously while focus driving of the lens is performed, high-precision focus driving control cannot be expected in the initial stage of the focus driving.